Conversion from 40 to 357 (conversely 357 to 40) should be a change of barrel only. I believe Steyr M/S A1 series are designed just like Sig 40's and 357. You simply switch barrels (in same model). Spring tension should come into play depending on ammo (if you reload - make sure it's strong enough to cycle the slide.) Although there are no after market barrels for Steyr M/S A1 being made locally (there is one made in Austria I think that was posted awhile back) that I know of , It's just a matter of time and we will see those local barrel maker's like Bar-Sto etc. will start making it. I hope there would be enough demand soon. Switching from a 9 to 40/357 is a whole lot different because of many factors notably ballistics and ammo size/shape - need to change mags, ejector, extractor, slide etc. and of course barrel - It's not practical.